Protective cellulose foil



Patented Sept. 1, 1936 PATENT OFFICE PROTECTIVE CELLULOSE FOIL Hans Isaac Schulz and Julius Appel, Bomlitz,

near Walsrode, Germany No Drawing.

Application November 2, 1935,.

Serial No. 48,055. In Germany March 7, 1932 3 Claims.

It has been found advantageous to provide advertising placards, such as are hung out in railway cars, shop-windows or taverns, with a brilliant coating layer improving the colour effect and allowing an easy cleaning of the placards.

Hitherto, these brilliant placards are manufac tured either by lacquering the printed layers by means of alcoholic varnishes whereby, however, the protective coating becomes irregularly brilliant and very delicate, or by applying to the papers a transparent ioil of celluloid whereby, it is true, a practically satisfying protective coating is obtained, but also the dangerous storing of more or less large quantities of easily inflammable foils of celluloid is necessitated. Also the coating of the papers with the not inflammable foils of acetyl cellulose involves difiiculties because the working by means of heat, necessary in this case, provokes a smelting of the whole mass of the protective foil of acetyl cellulose which easily adheres in this state to the coating tools and soils same. Furthermore it has been attempted to employ foils of cellulose which do not melt in the heat for coating purposes by impregnating these foils on both their sides with special varnishes and by uniting then the lacquered foils with the placard, but this method requires the use of expensive machines of complicated construction and, moreover, provokes considerable losses of material because these heat coating machines suppose a determined Working breadth of the protective foils and therefore, always leaves unused, according to the size of the placards, a more or less large strip on the edge of the foils.

The invention has now in view to solve the problem of manufacturing a protective foil which avoids the drawbacks of the hitherto known methods of coating papers and the like. To this end; the protective'ioil consists, according to the invention of a cellulose foil which is coated with a layer becoming adhesive and plastic in the warm but being at ordinary temperature solid and not sticky, which layer is applied preferably only to one side of the foil. Such a protective foil can be durably attached to posters, drawings, labels, geographical maps, pictures or other inscribed, printed or painted papers or other foundation materials without the aid of special apparatus and merely by smoothing it with a moderately warm iron and it imparts to these foundation materials a surface showing the desired brilliancy and which can be cleaned when necessary by dusting off or mopping up without being scratched. Furthermore the use of such protective foils is economical because the operator can himself out the pieces to the required sizes and thus utilize the sheet of foil to the best advantage. A further advantage of these foils consists in that the cellulose layer which is turned away from the poster or other substratum during the pasting on and to which 5 the heat iron is applied is infusible so that, during the action of the iron, only the coating layer which is turned towards the substratum becomes sticky and plastic and serves for uniting the cellulose foil to the substratum.

The cellulose foil employed for the purpose of the invention may be a transparent foil of cellulose hydrate which may be colourless or coloured. Also parchment paper, pergamyne or other transparent or translucent papers may be used, for instance, when lustreless surface effects are desired. It is also advantageous to employ foils of cellulose hydrate provided with a waterproof lacquer coating on one side or on both the sides. The applying of the adhesive layer can be effected to all these foils by means of a lacquering roller machine or of a spraying device or even by hand. The thickness of the coating layer being solid at the ordinary temperature of about 20 Celsius and becoming adhesive only in the warm may be 0.01mm. to 0.1 mm, preferably 0.03 mm. whilst the cellulose foil to be coated with this layer may possess a thickness of 0.02 mm. to 0.04 mm., mostly of 0.025 mm.

The coating layer may consist of a cellulose derivative, for instance of a cellulose ester or cellulose ether, with or without the addition of plasticizers or resins or of resins as well as of plasticizers. Also synthetic or natural resins or polymerization products or condensation products may be employed as coating mass with or without the addition of plasticizers, oils or similar substances. All these substances must show the property of becoming plastic in the warm and exerting then a sticking but being at ordinary temperature solid and not tacky. For the purpose of applying, these masses may be dissolved by means of suitable solvents or they may be brought by means of heat into a softened or molten state. The cellulose foil provided with the coating layer is rolled up after the drying and cooling or is immediately cut to appropriate sizes. The protective foil is then fit for immediate use and can be delivered to the consumer according to requirement. The consumer can 5 unite firmly and durably the protective foil with the substratum to be coated simply by pressing down it with a hot iron.

It is advantageous to employ a cellulose derivative of low viscosity, for instance, a cellulose ether or a cellulose ester of low viscosity for forming the adhesive layer. The use of a cellulose derivative of low viscosity provokes. a low softening temperature and an easy flowing of the adhesive layer when the protective foil is applied to the substratum, and, furthermore, the obtaining of a sure attachment of this foil to the substratum is facilitated. If additions of resins and plasticizers are used, these additions are adjusted so that, when melted, the cellulose derivative is retained in solution therein and no cloudinesses or precipitations in the coating film appear on the cellulose foil. It is preferable to select a resin whicheither in itself or in association with the plasticizer dissolves the cellulose derivative in the melt. Furthermore, it is preferable to employ a plasticizer having a high solvent capacity for the cellulose derivative concerned.

The optimum relative proportions of the components of the adhesive layer consisting of cellulose derivate of low viscosity, resin and plasticizer may vary somewhat according to the nature of the several constituents employed, but the quantities referred to the dry matter of the coating layer should be approximately from 30 to 60% of cellulose derivative of low viscosity, from 10 to 60% of natural -or synthetic resin and from 15 to 50% of plasticizer. The ratio of the amount of cellulose derivative to the amount of the mixture of resin and plasticizer preferably ranges between about 60:40 and 40:60 or 30:70, calculated upon the total amount of these three components. If the resin possesses in the liquid condition a sufiiciently high solvent power for the cellulose derivative, such as is, for example, the case with certain resins for nitrocellulose, the plasticizer may be entirely omitted and the coating layer made up on the basis of cellulose derivative and resin only.

If nitrocellulose is employed as the cellulose derivative for the coating layer, it is preferable to select a nitrocellulose of low viscosity, particularly the type E 510 or E 620, which is kept in clear solution in the warm by means of a mixture of ester resins and tricresylphosphate or of polyvinylacetate and dibutylphthalate, for example, at temperatures from to or from to Celsius such having been found suitable for applying protective foils according to the invention to foundations. Suitable types of nitrocellulose of low viscosity-when such are employed-are preferably such as exhibit a viscosity between 0.5 and 9 poisesc. g. s. unitsat 20 Celsius when measured in a 10% solution in pure butyl acetate. A nitrocellulose showing a viscosity of 2 poises in this solution is above all advantageous. The coating masses containing such nitrocelluloses have viscosities between 10 and.100 poises, particularly a viscosity of 30 poises, at 20 Celsius. Cellulose ethers of low viscosity and such cellulose esters with organic acid radicles, already display in themselves a higher plasticity than nitrocellulose, and consequently when they are employed the viscosity may be slightly higher, for instance, up to 10 poises in a 10% solution than in the case of nitrocelluloses.

When coating posters showing quite White or very pale colours or similar foundations with transparent protective foils, the mass which becomes adhesive in the warm and is to be applied in a very thin layer to the cellulose foil must be as colourless as possible so that the substratum is visible in its real colours through the protective foil applied thereto. In order to realize this condition which is desirable also in other cases for obtaining a satisfying transparence of the protective foil, the coating mass must be composed'of constituents which produce after the evaporation of the solvent a coating layer as clear as glass upon the cellulose foil. Therefore, when using nitrocelluloses, it is advantageous to select an extremely high-bleached collodion wool. Furthermore, it is of importance that the coating layer applied to the cellulose foil is free from waxes because an addition of wax provokes a reduction of the adhesive power and of the binding capacity of the coating layer in hot condition, which efiect is incompatible with a protective foil which must be firmly adhered to the substratum.

The production of a coating layer as clear as glass upon the transparent cellulose foil depends also on the nature of the resin contained in the coating mass. It has been found advantageous to specially select the commercial resins, for instance, dammar resins for the purposes of the invention and to free them from their colour constituents before use. There may be employed above all the resin type known in commerce under the name of Batavia dammar A which is freed from its colour constituents and at the same time also from wax additions in the following way: 10 kg. of this resin are finely broken and dissolved in a kneading apparatus together with 2.5 kg. toluol to a thick paste. When the mass has been completely dissolved which is the case after 2 to 3 hours, the wax is precipitated by adding 7.5 kg. ethyl-alcohol. Because the filtering causes certain difficulties, one decants during several days and extracts the clear solution.

The yield is 16 kg. solution with 48% content of purified dammar resin.

Owing to their clearness, also the perfectly colourless polymerization products prepared from vinyl esters or from esters of acrylic acid and the condensation products, for instance, the products of condensation of urea with formaldehyde are specially suitable for producing the coating layer to be applied to cellulose foils according to the invention. Furthermore, in order to save solvents and to increase the working speed of the applying of the coating layer to the cellulose foil, it is advantageous to employ solutions having a high content of dry matter which may be more than 30%, preferably 50% of the solution.

Examples 1. An endless foil of cellulose-hydrate which is provided with a Waterproof lacquer coating on one side or on both the sides is coated on the one side by means of lacquering coating machine The coating layer is applied in such a thickness that the dried coating film covering the cellulosehydrate foil has a thickness of 0.05 mm. After the cooling of the coating film, the cellulosehydrate foil is rolled up in the usual way or it is cut to the required sizes and is then fit for immediate, use. The attaching of the protective foil to the substratum can be effected by means of a hot iron having a surface temperature of about to 120 Celsius.

Percent 2. Nitrocellulose of low viscosity 21 Cyclo-hexanone resin 14 Tricresylphosphate 21 Alcohol 6.9 Toluene 10 Ethyl a'cetate 27.1

are mixed together so as to form a homogeneous solution which is then applied by means of a pouring device to a cellulose-hydrate foil having a thickness of 0.025 mm. The solution has a viscosity of 10.8 poises, measured at 20 Celsius, and the lacquer film resulting after evaporation of the solvent has a thickness of about 0.02 mm. The cellulose-hydrate foil provided with the lacquer film can be easily united between hot cylinders with posters, papers and the like at about Celsius and imparts a surface of high brilliancy to these foundations.

Percent 3. Acetyl cellulose of low viscosity 15 Diamylphthalate 15 Glycerine phthalic acid resin 3 Acetone 32 Ethyl acetate 28 Alcohol 7 are mixed together to form a homogeneous solution which is employed in the same manner as the mixture of Example 1.

Percent 4. Benzyl cellulose of low viscosity 13 Dammar resin 10 Dibutylphthalate 5 Toluene 65 Alcohol 7 are mixed together. The formed homogeneous solution is applied to a cellulose-hydrate foil. The thickness of the lacquer layer is 0.04 mm. The protective foil thus produced shows a high adhesive capacity at 100 to Celsius.

Percent 5. Collodion wool of low viscosity 21 Polyvinyl acetate resin of low viscosity" 14 Dibutylphthalate 15 Ethyl-alcohol 15 Ethyl acetate 25 Toluene 10 are mixed together and give a lacquer solution with a viscosity of 9 poises, measured at 20 Celsius. This solution is used as coating mass for transforming a cellulose-hydrate foil into a protective foil in the same manner as the mixture of Example 1.

Percent 6. Nitrocellulose of low viscosity 20.4

Dammar resin, purified 14.6

Dibutylphthalate 12.2

Toluene-alcohol 13.4

Toluene 22.4 Acetic ether 17 Percent 7. Nitrocellulose of low viscosity 22 Glycol-resin-ester 13 Dibutylphthalate 13.2 Alcohol 13.4 Toluene 21.4 Ethyl acetate 17 are mixed together. The lacquer thus obtained contains, calculated upon the dry matter, 46% nitrocellulose and 54% resin-plasticizer. It is applied by means of a spreading machine upon posters, paperboards, leather and other foundations.

Percent 8. Nitrocellulose of low viscosity 21 Polyvinyl acetate resin 14 Dibutylphthalate 13 Alcohol l5 Ethyl acetate 27 Toluene 10 are mixed together. The lacquer thus obtained can be employed in the same manner as the solution of Example 1. Owing to the clear vinyl acetate resin contained therein, this lacquer is characterized by an absolute colourlessness and therefore, it is suitable particularly for the manufacturing of protective foils serving for coating White or bright substratum surfaces. The dry matter content of this lacquer is 48% and the ratio of the amount of cellulose derivative to the amount of the mixture of resin and plasticizer is 44:56.

9. A lacquer of a very high concentration is obtained by mixing together Percent Nitrocellulose of low viscosity 26 Dammar resin 8 Amylphthalate 17 Alcohol 10 Ethyl acetate 27 Toluene 12 The ratio of the'amount of cellulose derivative to the amount of the mixture of resin and plasticizer is 51:49 in this lacquer which may be employed in the same manner as the solution of Example 1 for coating a cellulose foil.

Percent 10. Nitrocellulose of low viscosity 10 Dammar resin 20 Tricresylphosphate 6 Alcohol 10 Ethyl acetate 32 Toluene 22 are mixed together to form a homogeneous solution. This mixture produces when applied to a cellulose foil and cooled thereon a layer having a specially high plasticity and showing already at low temperature an efficacious adhesive power. The ratio of the amount of cellulose derivative to the amount of the mixture of resin and plasticizer is 28:72 in this coating mass.

Percent face thereof having a transparent, thermoplastic 11. Benzyl cellulose of low viscosity 12.7 layer having a thickness of .01 to .1 mm. compris- Glycerine phthalic acid resin 19 ing a cellulose derivative of low viscosity, a trans- Toluene 60.3 parent resin and a plasticizer, the ratio, of the Alcohol 8 amount of cellulose derivative to the amount of are mixed together. The lacquer thus obtained gives when applied to cellulose-hydrate foils and cooled thereon also an easily plastic layer which enables the cellulose-hydrate foils to be united with the foundation already at a temperature of about Celsius.

Percent 12. Acetyl cellulose of low viscosity 15 Dimethylphthalate 15 Glycol phthalic acid 'resin 3 Acetone 32 Ethyl acetate 28 Alcohol 7 are mixed together so as to form a homogeneous solution. This lacquer is applied in the same manner as the solution of Example 1 to cellulosehydrate foils in a layer of such a thickness that the dried coating film united with the cellulose foil has a final thickness of 0.02 mm. and becomes plastic under pressure at about Cel-.

sius.

13. An endless foil of parchment paper which is artificially veined like wood by printing or otherwise is coated on its one side with a molten layer composed of Percent Ethyl cellulose 30 Tricresylphosphate 25 Resin 45 The final dried coating film formed from this mass has a thickness of 0.03 mm. After the cooling and solidification of the coating film, the parchment foil is rolled up or cut to the required sizes. The protective foil thus obtained is attached to the substratum of wood, pasteboard or metal by smoothing it with a hot iron and imparts, then, to the substratum the appearance of a wood plate.

Of course, the invention may be realized. in detail also in a manner differing from the described examples.

What we claim is:

1. A protective, transparent foil adapted to be united by application of heat to a placard or other base material comprising a. transparent cellulose foil having one face thereof covered with a trans parent layer of waterproof lacquer and the other mixture of resin and plasticizer being substan: tially 60:40 so that when the said thermoplastic layer is melted no cloudiness or precipitation appears therein, said waterproof lacquer being infusible at the operating temperature at which the said thermoplastic layer becomes softened and at which the said foil is united to the base material.

2. A protective, transparent foil adapted to be united by application of heat to a placard or other base material comprising a transparent cellulose foil having one face thereof covered with a transparent layer of waterproof lacquer and the other face thereof having a transparent, thermoplastic layer having a thickness of .01 to .1 mm. comprising a cellulose derivativev of low viscosity, a transparent dewaxed dammar resin and a plasticizer, the ratio of the amount of cellulose derivative to the amount of mixture of resin and plasticizer being substantially 60:40 so that when the said thermoplastic layer is melted no cloudiness or precipitation appears therein, said waterproof lacquer being infusible at the operating temperature at which the said thermoplastic layer becomes softened and at which the said foil is united to the base material.

3. A protective transparent foil adapted to be united by the application of heat to a placard or other base material comprising a transparent cellulose foil having one face thereof covered with a transparent layer of waterproof lacquer and the other face thereof having a transparent thermoplastic layer having a thickness of from .01 to .1 mm. comprising nitro-cellulose having a viscosity between 0.5 and 9 poises at 20 degrees C. when measured in the form of a 10% solution in pure butyl acetate, a transparent dewaxed dammar resin and a dibutylpthalate plasticizer, the ratio of the amount of mixture of resin and plasticizer being substantially 60:40 so that when the thermoplastic layer is melted no cloudiness or precipitation appears therein, said waterproof lacquer being infusible at the operating temperature at which the said thermoplastic layer becomes sofbase material.

HANS ISAAC SCHULZ. JULIUS APPEL. 

